In the conventional preparation of a photovoltaic solar cell a PN junction is formed by diffusing either boron or phosphorus into a silicon base material. The silicon base material may be obtained pre-doped so that it is either P type or N type and the opposite type dopant is used in the junction formation process. These diffusions are generally made from a vapor phase in a vacuum or in a non-oxidizing atmosphere such as nitrogen or argon as a carrier gas at temperatures of 850.degree. C. to 1100.degree. C.
In making the solar cells a separate step is needed to apply a quarter-wave optical thickness antireflective film to the surface of the cell to make it more efficient. The antireflective coating increases the efficiency of the cell, for example, as much as 50 percent. Such optical coatings are applied by vacuum deposition, sputtering, or other techniques. Recently it was discovered that polymerized titanium dioxide solutions could be made which would deposit optical coatings of the desired thickness and index of refraction by liquid application methods. See U.S. patent application Ser. No. 931,346 filed Aug. 8, 1978 by Bulent E. Yoldas titled "Polymerized Solutions for Depositing Optical Oxide Coatings," now abandoned in favor of continuation application Ser. No. 065,706, filed Aug. 10, 1979. This new method reduced the cost of the anti-reflective application for solar cells.